An interesting thread on Twitter by Carl T. Bergstrom, Professor of Biology in Seattle.

A common train of thought is that we should let the virus "do its thing" as most of us are going to get it eventually - herd immunity - and the sooner we get it over with, the better for the economy.

There are several obvious objections to this idea, and one less obvious one which he points out.

I will start with the obvious: 1/ we don't want to overwhelm the NHS - beds/ventilators/PPE/experienced staff. As we have seen, even apparently simple things like PPE can cause huge problems. As to training up all the staff needed to manage all those patients in the Nightingale Hospitals - wow.
2/ if we flatten the curve, even if the numbers under the curve are the same, at least people are dying later, even if it is "only" months.
3/ those months might mean that drugs/a vaccine becomes available.

And the less obvious? To achieve herd immunity, a certain % of the population needs to have been infected, depending on R nought. The higher R nought, the higher the %. For an R nought of 2 it is 50%, for 4 it is 75%.
But the epidemic does not just stop when you achieve the herd immunity threshold - those still in the process of becoming infected still become infected, so there is overshoot. The higher R nought, the greater this overshoot - so that even if the herd immunity threshold is say 60%, the overshoot might mean a total of 80 % become infected - and all the extra deaths that would involve. Remember R nought is a variable over which we have partial control, via social distancing for example. And herd immunity is achieved when the number of daily infections is at its highest, so overshoot is easy to understand.

So the numbers are not the same when you flatten the curve, even if you ignore NHS overload/life prolongation/drug and vaccine development.

To make it clear, I am not at all an advocate of herd immunity as a strategy - it will happen of course, but we should be flattening that curve as much as possible - it will save lives, and nothing is worse for the economy than continuing large numbers of deaths, and a fearful public.